1. Field of the Invention
The present invention relates to catalysts for use in chemical reactions. More specifically, the present invention relates to a pretreated catalyst for use in reactions such as a process for producing an oxirane by reacting an olefin and a peroxide compound in the presence of the pretreated catalyst. Even more specifically, the present invention relates to, for example, a process for epoxidizing allyl chloride to epichlorohydrin using the pretreated catalyst such as a pretreated titanium silicalite catalyst.
2. Description of Background and Related Art
The reaction of epoxidizing allyl chloride to epichlorohydrin using a titanium silicalite catalyst and hydrogen peroxide (H2O2) is a well known process such as disclosed in, for example, U.S. Pat. No. 7,323,578. To date, the known processes for epoxidizing allyl chloride to epichlorohydrin have not been commercialized.
It is also well known that methanol is a necessary reaction component of the process of epoxidizing allyl chloride to epichlorohydrin to obtain high activity with a titanium silicalite catalyst; and typically, in such known processes methanol is used in large excesses (50-90 weight percent) to ensure that the reaction mixture remains as one liquid phase. However, the use of a large excess of methanol results in the formation of byproducts from the reactions of methanol and water, which are solubilized in the organic phase by methanol, with epichlorohydrin. These large quantities of methanol also result in estimations of large towers and high energy consumption for predicted purification on a commercial scale.
In addition, problems of low olefin selectivity and of difficult separations exist in the known processes; however, such problems can be solved by reducing the methanol concentration or removing methanol entirely from the processes. Still, in the epoxidation of many olefins, reducing or eliminating methanol concentration in the known processes creates a reaction system with two liquid phases, which results in lower epoxide yield, lower H2O2 selectivity to epichlorohydrin, and/or longer reaction times.
Chinese Patent Application No. CN 200710039080.1 describes reaction conditions for epoxidizing allyl chloride to epichlorohydrin with titanium silicalite and H2O2 without the presence of any solvent, including methanol. The teachings of CN 200710039080.1 include a molar ratio of allyl chloride to H2O2 from 1-100:1, a weight ratio of H2O2 to catalyst from 0.2-200, reaction temperatures from 25-100° C., pressures from 0.1-0.2 MPa, and reaction times from 0.1-48 hours. The catalyst used is titanium silicalite and the ratio of SiO2/TiO2 is 10-200. The examples described in CN 200710039080.1 have H2O2 conversions greater than 95 percent (%) and H2O2 to epichlorohydrin selectivities greater than 92%. However, using commercially available titanium silicalite catalyst under the conditions given in CN 200710039080.1 results in a H2O2 to epichlorohydrin selectivity as low as 81%. CN 200710039080.1 mentions that its “solvent-less system” simplifies and reduces energy consumption in the separation and purification of the products, but CN 200710039080.1 does not provide any examples or evidence of energy reduction using its process.